This invention relates to an automatic sensitivity controller for use in an electronic still camera system which performs flash photography.
In a photography process of taking a picture of a subject by using an electronic camera in a movie mode while continuously irradiating the subject with light, a low-band luminance signal Y.sub.L is extracted from a video signal which is output from an image pickup device such as a CCD via an AGC (automatic gain control) circuit, and is supplied (as a feedback) to a gain control terminal of the AGC circuit via a detection circuit so that the level of the output from the AGC circuit becomes generally constant.
In still-mode flash photography, it is not possible to adjust the gain of the AGC circuit since the light emission time is very short and, therefore, this gain is preset and fixed to a standard value.
However, if a small-emission electronic flash such as an electronic flash incorporated in a camera body is used to perform flash photography, the range of the photographable camera-to-subject distance is considerably restricted.
If, as in an ordinary case, the equivalent guide number is 12 and if the aperture value ranges from F2.8 to F16, the range of this distance L is 0.75 to 4.3 m and is thus narrow.
If a large-emission type of electronic flash is incorporated in the electronic camera in order to widen this range, the overall size of the camera as well as the manufacturing cost is increased.